In my U.S. application Ser. No. 606,093, filed Aug. 20, 1975, now U.S. Pat. No. 4,004,716 of Jan. 25, 1977, I have described and claimed a depositor for effecting simultaneous deposition of two different confectionery materials into a mold beneath it, the depositor comprising separate hoppers disposed out of contact with one another for the reception of the two materials, an independently controllable heater associated with each hopper, conduits extending from the hoppers to coaxially disposed inner and outer nozzles disposed beneath the hoppers, pumping mechanism for discharging material from one hopper through one conduit to the inner nozzle and from the other hopper through the other conduit to the outer nozzle, and a pad of thermal insulation disposed between the two conduits immediately above the coaxially disposed nozzles.
This depositor is primarily intended for depositing hard candy through the outer nozzle and a softer filling through the inner nozzle and the purpose of using separate hoppers, each with an independently controllable heater, for the different confectionery materials is to enable each material to be deposited at the temperature appropriate for it.
The purpose of the pad of thermal insulation is to reduce passage of heat by conduction from the material flowing through the outer nozzle to that flowing through the inner nozzle and so to minimize the risk of the material constituting the center of the deposit being subsequently raised to boiling point and bursting through the shell.
In the depositor specifically described and illustrated in the noted patent, the inner nozzle is a downward extension of the barrel of the pump by which the center-forming material is discharged into the mold and the thermal insulation is constituted by a disc of material disposed between the lower end of the barrel and the nozzle assembly. Such insulation prevents heat being conducted to the center material in the hopper but is ineffective to prevent heat from passing by conduction, through the wall of the inner nozzle, from the material flowing through the surrounding outer nozzle to that flowing through the inner nozzle.
When such a depositor is used to deposit hard candy with a filling of jam or other water-based material, the conditions of operation are especially critical. The hard candy is deposited at a temperature of approximately 140.degree. C, while the jam cannot be deposited at a temperature lower than about 55.degree. C, because otherwise it will not flow satisfactorily. When, as a typical case, the shell of hard candy constitutes two thirds of the volume of the deposit and the filling of jam the remaining third, the temperature at the interface between the shell and the filling is 111.degree. C when the above depositing temperatures are used. The boiling temperature of the jam is, however, 115.degree. C.
The depositor is accordingly operating under conditions very close to the safety limit. There is accordingly a risk of boiling of the filling at the interface with the shell should, for example, the boiling point of the jam be reduced as a result of change in the recipe. More seriously, there is a tendency for the temperature of deposit of the jam to rise after the depositor has been in continuous operation for a sufficient time due to conduction of heat to the jam through the wall of the inner nozzle as it flows through the inner nozzle, from the candy flowing past the outer wall of the inner nozzle, causing the interface temperature to exceed the boiling point of the jam.